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BMS > Cell Membrane and Cell Polarity > Flashcards

Cell Membrane and Cell Polarity Flashcards

1
Q

Part of the plasma membrane which creates a barrier to most water soluble molecules

A

Lipids

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2
Q

Make up roughly 30% of the genome

A

Transmembrane proteins

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3
Q

The lipid and protein interactions in the plasma membrane are

A

Non-covalent

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4
Q

Proteins and lipids can often move in the

A

Bilayer

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5
Q

What are the four classes of membrane lipids?

A
  1. ) Phosphoglycerides
  2. ) Sphingolipids
  3. ) Glycolipids
  4. ) Sterols
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6
Q

Derived from 3-carbon glycerol backbone with 2 fatty acid chains attached to backbone

-There are three major types

A

Phosphoglycerides

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7
Q

Derived from sphingosine backbones

-Sphingomyelin is a major one

A

Sphingolipids

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8
Q

Often a sphingosene backbone with carbohydrates on the external face

A

Glycolipids

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9
Q

The four major classes of membrane lipids make up what percentage of the membrane mass?

A

50%

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10
Q

Their structure allows them to assemble into a bilayer which insulates the cell from the environment

A

Lipids

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11
Q

Amphipathic membrane lipids assemble spontaneously

into lipid bilayers and then into

A

Liposomes

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12
Q

Lipids in solution will first form a bilayer, with hydrophobic regions insulated from water, then free edges will associate to form a

A

Liposome

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13
Q

One chain lipids in solution will form

A

Micelles

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14
Q

What is the basic structure of a phosphoglyceride?

A

head group, then a phosphate, glycerol, and 2 hydrocarbon tails

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15
Q

Two fatty acid chains attach to two of the three carbons of the

A

Glycerol backbone

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16
Q

Importantly, one of the two chains is typically

-opposes dense packing and leads to membrane fluidity

A

Unsaturated (has a double bond)

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17
Q

The three major phospholipid groups of the plasma membrane are named according to their head groups. What are they?

A
  1. ) Phosphatidyl Ethanolamine
  2. ) Phosphatidyl Serine
  3. ) Phosphatidyl Choline
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18
Q

Has a net negative charge

A

Phosphatidyl Serine

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19
Q

What are the five major lipids of the plasma membrane?

A
  1. ) Phosphatidyl Ethanolamine
  2. ) Phosphatidyl Serine
  3. ) Phosphatidyl Choline
  4. ) Sphingomyelin
  5. ) Sphingosine
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20
Q

Stiffens regions of the plasma membrane in its vicinity

-found in both leaflets of plasma membrane

A

Cholesterol

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21
Q

Its aliphatic regions keep phospholipid chains apart

A

Cholesterol

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22
Q

How many types of glycolipids are there?

A

40 types

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23
Q

Charged glycolipids

A

Gangliosides

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24
Q

Derived from sphingosine but have sugars added rather than phosphate

A

Glyclipids

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25
Q

Asymmetric, meaning that their sugar is present only on the external face of the plasma membrane

A

Glycolipids

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26
Q

GM1 ganglioside is used for entry of

A

Cholera toxin

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27
Q

Lipid composition of specific membranes can vary by both membrane type and

A

Cell type

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28
Q

Primarily located in plasma membranes (less internal)

A

Cholesterol and sphingomeylin

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29
Q

Enriched in intracellular membranes such as in mitochondria or endoplasmic reticulum

A

Phosphatidylethanolamine and phosphatidylcholine

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30
Q

Located in the plasma membrane and enriched in meylin, but there are little in the internal membranes

A

Glycolipids

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31
Q

Lipids laterally diffuse in both inner and outer

layers but rarely

A

Flip between leaflets

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32
Q

Absent from bacteria and plants

A

Cholesterol

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33
Q

Subdomains of the plasma membrane that contain high concentrations of cholesterol and glycosphingolipids. They exist as distinct liquid-ordered regions of the membrane that are resistant to extraction with nonionic detergents

A

Lipid rafts

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34
Q

Plasma membrane lipids are asymmetrically distributed between

A

Internal and external faces

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35
Q

Which lipids typically make up the inner leaflet?

A

Phosphatidylethanolamine and phosphatidyl serine

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36
Q

Which lipids typically make up the outer leaflet?

A

Sphingolipids, glycolipids, and phosphotidylcholine

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37
Q

Areas of non-random lipid distribution within inner or outer membrane leaflet

A

Lipid Rafts

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38
Q

Lipids can non-randomly associate in “rafts” enriched in cholesterol and sphingomeylin. They can sequester subsets of

A

Membrane proteins

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39
Q

There are many thousands of

A

Minor lipids

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40
Q

An example of a “minor” lipid that is now known to have amajor role in signaling

A

Phosphotidylinositol (PI)

41
Q

Phosphotidylinositol serves as a dock for downstream signaling molecules and is a precursor to soluble

A

IP3

42
Q

Membrane proteins can be either

A

Integral or Peripheral

43
Q

Incorporated into membrane with stretches of hydrophobic amino acids that are arranged in either alpha helices of 15-20 aa or barrels, with hydrophilic aa buried

A

Integral membrane proteins

44
Q

Some “integral” proteins have a lipid covalently attached that can reversibly interact with the

-Are not true integral proteins

A

Membrane

45
Q

Usually associate with the membrane through non-covalent interactions (like electrostatic interactions)

A

Peripheral membrane proteins

46
Q

Serve as signaling molecule, adhesion, receptors, and transport

A

Membrane proteins

47
Q

Proteins can be post-translationally bound to several types of lipids that then mediate association with the

A

Membrane

48
Q

Membrane proteins can be immobilized by the underlying

A

Cytoskeleton

49
Q

Membrane proteins often diffuse within the membrane

but can be anchored to

A

Cytoskeleton

50
Q

Cytoskeletal protein spectrin is a dimer attached indirectly (via intermediates) to the transmembrane proteins

A

Glycophorin and/or band 3

51
Q

Create a barrier to transport of many molecules, especially ions and small molecules

A

Membrane lipids

52
Q

What are the three distinct types of molecules that serve as transporters across the membrane?

A
  1. ) Pumps
  2. ) Carriers
  3. ) Channels
53
Q

Moves ions/molecules uphill, or against the gradient, and into or out of the cell

-highly specific

A

Pumps

54
Q

Pumps require

A

Energy

55
Q

Have an intermediate specificity and serve to help molecules/ions to move down their gradients (downhill) into/out of the cell

A

Carriers

56
Q

Do carriers require energy input?

A

No

57
Q

Not very specific and serve to allow molecules to freely flow down their gradients without physically helping them

A

Channels

58
Q

Do channels require energy?

A

No

59
Q

Of the three transporters, which is the only one that can transport multiple ions per conformational change?

A

Channel

60
Q

Many disease states result from alterations in the levels or structure of

A

Transporters

61
Q

Channels and carriers are considered to be

A

Passive transport

62
Q

Ion-specific pores that open and close in a regulated manner

A

Channels

63
Q

Enzyme-like proteins that mediate passive transport down concentration gradients without chemical change

A

Carriers

64
Q

Enzymes that need energy to move ions and other solutes across the membrane against a concentration gradient; energy provided via ATP mediated phosphorylation or ATP binding and hydrolysis

A

Pumps

65
Q

Can promote or oppose ion movements driven by concentration gradients

-combine to produce electrochemical gradient

A

Membrane potential

66
Q

Regulation of pore opening (open/closed) alters ion flow and rejects inappropriate ion because of

A

Charge or Size

67
Q

Which two things block sodium channels

A

Tetrodoxin and lidocaine

68
Q

What are two potassium channel blockers?

A

Scorpion venum and cone snail toxins

69
Q

What are the three major “carrier-type” transporters

A

Uniport, symport, and antiport

70
Q

Carrier that allows passive transport down the concentration gradient

A

Uniport

71
Q

Coupled transport where the transport of one solute depends on the transport of another

A

Symport (same direction) and Antiport (opposite directions)

72
Q

In an antiport, the free energy release from a molecule moving down its concentration gradient can be used to

A

Drive the second transport step

73
Q

Undergo a random switch between states that sequentially open on both membrane sides whether or not solute is bound

-The end result is that solutes will move down concentration gradient at higher rate than by diffusion

A

Uniport Carrier transporters

74
Q

Carrier transporters will depend on concentration gradient and binding affinity similar to

A

Enzyme kinetics

75
Q

What is an example of a coupled carrier transporter?

A

Na-Glucose symporter

76
Q

Displays co-operative binding such that binding of Na+

increases affinity of symporter for glucose

A

Na-Glucose symporter

77
Q

Allows transport of glucose against concentration gradient without direct energy expenditure

-both sites need to be occupied for conformational switch to occur

A

Na-Glucose symporter

78
Q

Transcellular glucose transport from digestive system

through epithelial cell uses two

A

Glucose transporters

79
Q

The first step in moving glucose through epithelial cells is that Na+ moves down its gradient which

A

Drags glucose inside (Na-Glucose symporter)

80
Q

The second step in moving glucose through epithelial cells is that once inside the epithelial cell, glucose moves down its gradient through a

A

Different transporter

81
Q

To keep the system working properly, epithelial cells get rid of the sodium brought in with glucose using a

-ATP dependent pump

A

Na/K transporter on basal surface

82
Q

What are the three classes of ATP driven pumps?

A
  1. ) P-type
  2. ) F-type (and V-type)
  3. ) ABC transporter
83
Q

Multi-pass TM domains that autophosphorylate themselves resulting in a conformational change that pumps ions

A

P-type pump

84
Q

Has multiple subunits that uses H+ flux to drive ATP synthesis

-Also used to acidify vesicles

A

F-type (and V-type) pump

85
Q

ATP-driven pump that pumps small molecules rather than ions

A

ABC transporter

86
Q

One of the most important P-type transporters that keeps the Ca2+ concentration low in the cytosol

A

Ca2+ ATPase

87
Q

Makes up 90% of membrane protein in muscle cells

A

Ca2+ ATPase

88
Q

How does the Ca2+ TPase work?

A

Ca2+ binds non-phosphorylated transporter. This allows ATP to bind and phosphorylate the transporter which induces a conformational change that opens the channel to the lumen of the sarcoplasmic reticulum (SR) and releases Ca2+

89
Q

Another important P-type phosphorylator that uses 1/3 of the cellular energy

A

Na/K ATPase

90
Q

How does the Na/K ATPase work?

A

Na+ binds, phosphorylation induces conformational change that releases and allows K+ to bind. Dephosphorylation then induces another conformational change and K+ is released

91
Q

What is the net movement of the Na/K ATPase?

A

Moves 3 Na+ out and 2 K+ in

92
Q

Have two ATPase domains in each, and small molecules bind to the non-ATP bound state

-Abundant: can be 5% of genes in bacteria

A

ATP-binding-casettes (ABC transporters)

93
Q

In an ABC transporter, when ATP is bound, the two ATPase domains dimerize, which produces a conformational change that

A

Exposes substrate to the opposite side of the membrane

94
Q

ATP hydrolysis then releases the

A

Substrate

95
Q

There are over 100 of these in humans and they are clinically important

A

ABC transporters

96
Q

In multiple drug resistance (MDR), high levels of one type of ABC transporter can arise in tumor cells, which allows more hydrophobic drug to be cleared from cytoplasm so that

-occurs in 40% of cancers

A

Drug effects are reduced

97
Q

ATP binding to cystic fibrosis TM conductance regulator protein (CFTR) drives opening and closing of a

A

Cl- channel (and ABC transporter)

98
Q

Binds to acetylcholine receptor (Ach) and blocks nerve transmission

A

Curare

BMS (62 decks)

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